The potential of organic semiconductor-based devices for light generation is demonstrated by the commercialization of display technologies based on organic light-emitting diodes (OLEDs). Nonetheless, device complexity, efficient integration between frontplane and backplane components as well as exciton quenching and photon loss processes still limit OLED efficiency and brightness.
Organic light-emitting transistor (OLET) is a recently developed optoelectronic device that combines the switching mechanism of a thin-film transistor and an electroluminescent device. While charge transport occurs perpendicular to the organic layers in an OLED, the majority of the current flows horizontally through the semiconducting layers in an OLET. As a result, light in an OLET is emitted as a stripe along the emissive layer, rather than uniformly through the electrode areas as in conventional OLEDs. The planar transport geometry of OLETs helps suppress deleterious photon losses and exciton quenching mechanisms inherent in the OLED architecture. Accordingly, the same organic electroluminescent light-emitting material has been shown to achieve much higher external quantum efficiency (EQE) in an OLET than in an equivalent OLED.
In particular, a trilayer heterostructure OLET has been reported with a maximum EQE of about 5%. The reported trilayer heterostructure OLET includes, from bottom to top, a transparent substrate, a gate electrode, a gate dielectric, an active layer consisting of the superposition of three organic layers, and source and drain electrodes on top of the active layer. The trilayer active layer includes a light-emitting host-guest matrix sandwiched between an electron-transporting (n-type) semiconductor and a hole-transporting (p-type) semiconductor. However, because only a small portion of the current is converted into excitons, one area of weakness for this device structure is the limited brightness.
Accordingly, there is a need in the art to develop new OLET device structures that can provide improved brightness.